FIG. 22 is a cross-sectional view showing an essential part of a conventional pipe joint. A pipe joint 30 joins a pipe 31 to be joined and a pipe (not shown) to be joined thereto in a water-tight manner. A compressed packing ring 35 seals a space between a pipe joint body 32 fitted over both the pipes to be joined and the pipe 31. A pressing ring 33 is connected to the flange of the pipe joint body 32 by a tightening element 34 including a bolt and a nut. A lock ring 36 which is split at one point in the peripheral direction is contained within the pressing ring 33 on the inner peripheral side thereof. A piece ring 37 is interposed between the lock ring 36 and the packing ring 35.
At the time of piping, from a temporarily mounted state as shown in FIG. 23, the tightening element 34 is operated to move the pressing ring 33 toward the pipe joint body 32, and the packing ring 35 is then press-fitted into a containing section 32a of the pipe joint body 32 by being pressed by the pressing ring 33. As shown in FIG. 24, the packing ring 35 has a seal section 35a that has a circular cross section, a base section 35b that has a rectangular cross section, and a lip section 35c that is projection-shaped. The seal section 35a is press-fitted into the containing section 32a at the rear thereof. The base section 35b is arranged in the containing section 32a at the front thereof. The seal section 35a is larger than the rear of the containing section 32a. The compressed seal section 35a mainly makes contact with the pipe 31.
However, in the pipe joint having such a configuration, the packing ring 35 is compressed while being moved in the pipe axis direction. Therefore, the pipe 31 may be pulled when the packing ring 35 is press-fitted into the containing section 32a. Due to the pull of the pipe 31, in a sealed state shown in FIG. 22, the pipe 31 is dislocated by a distance L from the state of FIG. 23, resulting in changing of an insertion amount. For this reason, when the pipe joint is mounted, it is necessary to set the initial insertion amount to be somewhat smaller by taking the pull of the pipe into account.
A pipe joint described in Patent Document 1 listed below has a packing ring in which the minimum inside diameter at the time of non-pressing is set to be larger than the outside diameter of the pipe to be joined. However, as in the conventional pipe joint, to mount the pipe joint to create the sealed state, the packing ring is required to be compressed while being moved in the pipe axis direction by being pressed by a pressing ring. As a result, the pipe to be joined may also be pulled.
When such pull of the pipe to be joined occurs, the insertion resistance of the pipe to be joined is increased. Therefore, the piping efficiency can be deteriorated. In addition, to increase the piping efficiency, it is greatly advantageous that sealing is enabled by the packing ring while the initial insertion amount of the pipe to be joined is held. Therefore, a method which can prevent the pull of the pipe to be joined has been strongly desired.
In the pipe joint 30 in the temporarily mounted state shown in FIG. 23, the pressing ring 33 is connected to the pipe joint body 32 with a predetermined space, and between the pressing ring 33 and the pipe joint body 32, the packing ring 35, the lock ring 36, and the piece ring 37 are integrally held. From this state, the tightening element 34 is tightened to move the pressing ring 33 toward the pipe joint body 32. Then, as described above, the pressing ring 33 press-fits the packing ring 35 into the containing section 32a of the pipe joint body 32. And, the inner peripheral surface of the lock ring 36 reduced in diameter is engaged with the outer peripheral surface of the pipe 31.
Conventionally, to reduce the number of operations at a piping site, the pipe joint 30 which is previously temporarily mounted in an assembling factory is conveyed to the piping site, and the operator simply tightens the tightening element 34 at the piping site. However, when the tightening element 34 is tightened to accidentally compress the packing ring 35 due to vibration and the like at the time of conveyance, the sealing performance after the piping may be varied, with the result that the insertion of the pipe 31 into the pipe joint body 32 may be inhibited. Therefore, in the temporarily mounted pipe joint 30, it is important to regulate the advancing movement of the pressing ring 33 toward the pipe joint body 32.
Patent Document 2 listed below describes a pipe joint in which a spacer widened in the pipe axis direction is detachably engaged with a bolt which connects a joint body and a pressing ring, so that the advancing movement of the pressing ring toward the joint body can be regulated. However, in the pipe joint, the number of necessary spacers is increased according to the number of bolts, with the result that the number of components is increased. In addition, unpreferably, when the bolt is tightened to move the pressing ring toward the joint body, the detached spacer can be a nuisance to the operator.
Patent Document 3 listed below describes a pipe joint which has an interval regulation member provided between a separation prevention member and an elastic seal material. The interval regulation member regulates the interval between a socket pipe section and a pressing ring until the elastic seal material is brought into a set compression state and is sheared to release the interval regulation when the elastic seal material is brought into the set compression state. However, in the pipe joint, when the pressing ring is tightened and fixed onto the socket pipe section, the interval regulation member is sheared. In a case where the pipe joint is dismounted after the completion of piping due to some circumstances, the pipe joint cannot be reused as is.